Display Tagline on Mobile (Brine) Needed in A Font Weight of 500

Site URL: https://www.leannebebbington.co.uk

Hello!

Can anybody help me get the font weight (I think It's this) of my tagline to 500 in mobile view like I have on my desktop view? The font just needs to be a little bit more bold.

I used the below code: 

a.Mobile-bar-branding:after {
    content: "CONTENT CREATOR/SOCIAL MEDIA MANAGER";
    display: block;
    margin-top: 20px;
    font-weight: 500;
    font-size: 11px;
    font-family: FormaDJRDisplay; 
    color: #333;
}